Diseases among dairy herds dramatically impact the economics of animal production and milk production in the United States. It is estimated that the dairy cattle industry constitutes a significant contribution to the gross national product of the United States, accounting for an estimated $38 billion annually. A wide range of diseases, infections and injuries to the feet of animals, including cattle that are part of dairy herds, exist. Livestock in a dairy herd, for example, are susceptible to forming a variety of warts, abscesses, sole ulcers, foot rot, heel cracks and variations of lesions and infections on their feet and/or hooves, which may individually or collectively cause livestock to suffer lameness, clubbed hooves, loss of body weight, decreased milk production, and decreased rates of conception.
Infectious hoof diseases are common in farm animals such as sheep, goats, horses, dairy cows, and beef cattle. For example, hairy hoof warts, also referred to as digital dermatitis, hairy footwarts, strawberry or raspberry heelwarts or hairy heel warts, is a common disease condition in dairy cows and can cause lameness which leads to a decline in animal health and performance as measured by a decrease in body weight, fertility, and milk production. Since the late 1980's, bacterial diseases such as hairy heel warts have been a significant source of bovine lameness, and have had a significant economic impact on farmers.
Farmers have addressed this problem using a livestock footbath. The footbath holds a solution containing a substance to prevent and/or treat the disease, such as copper sulfate and/or zinc sulfate, or an antibiotic. Animals are forced to walk through the footbath to immerse the hooves in the treatment solution. For example, dairy cattle are usually led through a footbath on their way to or from the milking parlor. However, there are problems associated with the use of livestock footbaths, and they are not the most effective method of treatment and prevention of foot diseases. In particular, foot baths are inefficient and costly for at least one of the following reasons.
First, the length of the foot bath is directly correlated to the effectiveness of the treatment solution, with the longer the bath, the greater the duration of exposure to the treatment and prevention solution. The commonly used four foot long baths are not long enough for proper cleaning of the feet and subsequent exposure of the lesions to the treatment solution, especially since on average, animals walk through a traditional foot bath for five seconds or less. Moreover, manure attached to the animals hooves will commonly be carried into the foot bath or the animal may defecate into the foot bath, and since foot baths are liquid filled reservoirs that hold all environmental contaminants, the manure, mud and dirt rapidly degrade the treatment solution and render it ineffective. Also, most foot baths are permanently fixed and this prevents a farmer from locating the bath and treating the animals at different locations on the facility.
A further limitation to use of foot baths on farms is that they require a high level of management. The treatment solution requires changing at specified intervals after several animals pass through the bath in order to maintain efficacy of the treatment solution. If the foot bath is not changed and re-charged accordingly, the efficacy of the treatment solution is greatly reduced. On a practical level, animals experiencing foot problems generally walk slower and are the last animals through the foot bath, when the bath is at its most inefficient, thereby decreasing the effectiveness of the treatment. Yet another limitation associated with the use of foot baths is that many of the products available for the treatment and prevention of foot diseases are not labeled for use in foot bath applications and are difficult to get into solution, for example, copper sulfate and zinc sulfate. Other products, including antibiotics, are not easy to use in the context of a foot bath, especially due to their cost and the fact that antibiotics degrade quickly when exposed to organic material.
Moreover, such footbaths as described supra may also cause pollution and injury to animals and humans. For example, discharge of copper sulfate, a compound commonly used in treating cows, from bath treatment systems into adjacent lands may cause significant damage. This is because most dairies dump the spent foot baths into a manure pit or a lagoon and the copper ultimately gets spread on production ground with the manure. The practice can lead to copper accumulation in the soil and after several years can accumulate in soil to levels that become toxic to soil microbes and crops. This can slow organic matter decomposition and nutrient cycling in soil and crop production could be reduced because of direct toxic effects of copper on the plants as well as reduced soil fertility. Importantly, copper accumulation in soil and forage can become toxic to sheep, whose tolerance for copper is much lower than that of dairy cattle. Toxic levels of copper in soil is a critical issue because there is no practical way to reverse the problem. Moreover, many large dairy farms use anaerobic digesters to produce methane gas from manure, and when copper sulfate can inhibit the bacteria's ability to produce methane gas in a digester lagoon.
Another chemical used in foot baths by the dairy industry is formaldehyde. Numerous burns to humans and animals result annually from use of formaldehyde; loss of eyesight and even death among workers have occurred. For these reasons the European Union has called for a ban of its use, and in the United States it has been listed as a known carcinogen.
In view of the problems outlined supra, there is a need for improved compositions and methods for treating one or more infectious diseases of a foot of an animal, including hairy heel warts.